The present invention relates to a semiconductor laser and, more particularly, to a high optical output window structure semiconductor laser.
In a double heterojunction semiconductor laser, high optical power density emission was achieved with a so called window structure laser by forming a stripe-geometry exciting region in an active layer so as not to be exposed on the opposite reflective surfaces, and selecting a band gap of the stripe-geometry exciting region narrower than that of a pair of window regions or non-exciting regions formed between the respective reflective end surfaces and the tip ends of the exciting region. To make the band gap of the exciting region narrower than that of the window regions, a corresponding region of the heavily doped n-type active layer is changed into a p-type region by diffusing a p-type impurity such as zinc (see IEEE Journal of Quantum Electronics, vol. IE-IJ, No. 8, August 1979, pp. 775 to 781). This semiconductor laser, however, requires very fine and delicate control of the concentration and depth of the p-type impurity diffused region formed in the active layer, and that it has heretofore been difficult to obtain reproducibility with a good yield. In addition, since an impurity is heavily doped into the active layer a lattice defect is easily induced, which means that the reliability of the semiconductor laser of the type described above is unsatisfactory.